LIE:. -..-i.RY  of  tlrie 

Agriculttirai. 
College. 

Issued  October  21,  1908. 


U.  S.  DEPARTMENT    OF  AGRICULTURE, 

FOREST  SERVICE. 
GIFFORD  PINCHOT,  Forester. 


EXTENT  AND  IMPORTANCE  OF  THE 
CHESTNUT  BAM  DISEASE. 


By 

E.  E.  HODSON, 

FOBESX  ASSISTANT,    FOREST   SERVICE. 


WASHlPiUiTON  :  GOVERNMENT  PRINTING  OFFICE  :  1609 


CONTENTS 


Page. 

Introduction 3 

Manner  of  infection 3 

Symptoms 3 

Localities  affected 4 

How  the  disease  spreads 5 

Amount  of  damage 5 

Utilization  of  dead  and  diseased  trees , 6 

Measures  of  prevention 7 

(2) 


EXTENT  AND  IMPORTANCE  OF  THE  CHESTNUT  BARK 

DISEASE. 


INTBODTJCTION. 

Three  years  ago  a  destructive  fungous  disease  of  the  chestnut  first 
attracted  attention  and  almost  immediately  assumed  the  character 
of  an  epidemic.  It  seems  to  be  one  of  the  most  serious  diseases 
which  has  ever  attacked  an  American  forest  tree,  and  has  done  great 
damage  locally  in  and  around  New  York  City,  and  is  now  spreading 
rapidly  in  all  directions  to  forest  tracts  in  Connecticut,  New  York, 
New  Jersey,   and  even  into  Pennsylvania. 

The  disease  was  first  studied  by  Dr.  W.  A.  Murrill,  of  New  York, 
and  during  the  past  eighteen  months  it  has  been  under  investigation 
by  Dr.  Haven  Metcalf,  of  the  Bureau  of  Plant  Industry.  The  tech- 
nical details  given  in  this  circular  have  been  derived  chiefly  from  the 
publications  of  the  former  and  information  supplied  by  the  latter. 

MANNER  OF  INFECTION. 

The  disease  is  caused  by  a  fungus  known  as  Diaporthe  parasitica 
and  Valsonectria  parasitica,  the  spores  of  which  enter  the  tree 
through  wounds  on  branches  or  trunk.  Dead  twigs  also  offer  a 
means  of  entrance,  and  there  are  probably  other  ways,  not  yet 
known,  by  which  the  trees  become  infected. 

From  the  point  of  entrance  the  fungus  spreads  in  all  directions 
throughout  the  cambium  and  inner  bark  until  it  completely  girdles 
the  branch  or  trunk  it  has  attacked.  It  has  been  found  that  a  few 
of  the  outer  annual  rings  of  the  wood  are  also  attacked,  and  it  is  very 
likely  that  the  fungus  penetrates  some  of  the  medullary  rays  in 
search  of  the  food  material  wliich  they  contain;  but  the  real  seat  of 
the  injury  is  the  inner  bark  and  the  growing  layer  of  the  wood.- 

SYMPTOMS. 

When  a  tree  is  first  attacked  the  disease  is  not  noticeable,  and  is 
likely  to  be  overlooked.  In  many  instances  the  trees  are  attacked 
first  on  the  smaller  branches.  These  are  soon  girdled,  and  the  foliage 
turns  yellow  and  then  wilts.  By  these  wilted  branches  the  disease 
can  be  detected  from  a  distance.  The  girdled  branches  or  trees  do  not 
usually  die  until  the  second  year,  except  when  they  are  attacked 
very  early  in  the  season,  or  when  the  infected  limbs  are  small. 

(3) 


On  limbs  with  smooth  bark  the  diseased  patches  are  sunken  and 
discolored,  with  small  brownish  or  yellow  knobs  scattered  over  the 
surface.  On  the  edge  of  the  affected  area  in  the  growing  season 
there  is  a  ring  of  greenish,  yellowish,  or  bright  yellow  excrescences 
which  resemble  horns  and  are  very  conspicuous,  so  that  in  young 
trees  the  disease  is  easily  detected  even  before  the  branches  wilt.  In 
very  drj  weather,  however,  these  horns  may  be  nearly  or  entirely 
suppressed.  Where  the  bark  is  thick,  as  on  large  trees,  it  is  not 
changed  in  appearance,  but  the  brownish  knobs  of  the  fruiting  bodies 
show  in  the  cracks,  and  the  bark  sounds  hollow  when  struck. 

On  account  of  its  rapid  action  in  killing  or  wilting  small  branches, 
the  disease  can  not  remain  long  undetected  if  the  trees  are  under 
inspection.  At  the  end  of  a  single  year  the  disease  has  usually  made 
its  presence  conspicuous  by  a  large  number  of  dead  and  dying  trees. 

LOCALITIES    AFFECTED. 

In  1905  the  disease  had  already  spread  over  a  considerable  area 
around  New  York  City,  where  it  apparently  originated.  In  the 
present  year  it  is  spreading  rapidly  in  a  westerly  direction  over 
northern  New  Jersey,  where  in  Morris  County  large  tracts  have 
recently  been  attacked.  New  York  City  is  about  the  center  of  the 
infected  area.  Last  year  the  chestnut  tracts  in  Westchester  and 
Nassau  counties  in  New  York,  Fairfield  County  in  Connecticut,  and 
Bergen  County  in  New  Jersey  were  severely  attacked,  and  now  Morris, 
Essex,  and  Monmouth  counties,  N.  J.,  can  be  added. 

In  Connecticut  the  disease  is  very  severe  at  Stamford.  It  has  been 
found  near  Danbury  and  Waterbury,  and  is  known  to  extend  along 
the  coast  to  New  London.  It  is  also  reported  in  southeastern  Massa- 
chusetts and  as  far  north  as  Wellesley. 

On  Long  Island  it  is  common  in  the  western  part  and  along  the 
northern  shore  to  Huntington.  It  is  likely  that  it  occurs  on  the 
island  wherever  there  is  chestnut,  although  it  has  not  yet  been 
reported  from  the  eastern  end.  It  extends  up  the  Hudson  to  Pough- 
keepsie,  and  across  the  river  to  the  west;  it  has  been  found,  though 
not  in  great  abundance,  at  Turner  and  Warwick,  and  has  been 
reported  at  Marlborough.  Near  the  Connecticut  line  it  occurs  as 
far  north  as  Pawling  and  is  very  destructive  from  Katonah  all  the 
way  southward  to  New  York  City. 

In  New  Jersey  the  disease  is  very  abundant  in  the  northern  and 
eastern  parts,  particularly  near  the  coast  in  Bergen,  Essex,  and 
Monmouth  counties.  Southward  it  .is  found  along  the  Delaware 
Eiver  to  Trenton,  and  abundantly  along  the  coast  near  Chapel  Hill 
and  Eatontown  in  the  northern  part  of  Monmouth  County.  Recently 
a  belt  around  Morristown  and  German  Valley  has  become  badly 
infected,  and  the  disease  has  been  discovered  in  wild  trees  at  Newark 
and  Fenton,    Del.,    and  at  various  points   near  Philadelphia,   Pa. 


In  Pennsylvania  it  is  nowhere  abundant  yet,  although  it  exists  at 
Easton,  South  Bethlehem,  and  Morrisville,  and  is  reported  as  far 
north  as  the  Pocono  Mountains  and  as  far  south  now  as  Philadel- 
phia. It  has  also  been  found  near  Baltimore,  Md.,  and  in  Bedford 
County,  Va. 

The  range  at  present,  then,  includes  eight  States:  Connecticut, 
New  York,  New  Jersey,  Pennsylvania,  Delaware,  Maryland,  Virginia, 
and  Massachusetts.  Pennsylvania,  so  far  as  known,  is  not  infected 
to  any  great  extent,  except  on  the  eastern  border,  while  Massachu- 
setts, Maryland,  and  Virginia  are  touched  only  at  one  or  two  points. 

HOW  THE  DISEASE   SPREADS. 

The  yellow  fruiting  bodies  so  common  on  the  diseased  trees  are 
constantly  giving  off  millions  of  summer  spores  all  through  the 
growing  season.  These  are  transported  by  various  agencies  to 
healthy  trees,  where  they  gain  entrance  through  wounds  in  the  bark. 
Wind  is  probably  the  principal  agency,  but  the  spores  are  no  doubt 
carried  by  animals,  birds,  insects,  and  by  shipment  of  infected 
material. 

The  disease  spreads  locally  through  the  gradual  distribution  of 
the  spores  from  tree  to  tree,  and  at  a  distance  chiefly  through  the 
shipment  of  infected  material,  such  as  nursery  stock,  bark,  nuts,  and 
other  products.  There  is  a  possibility  that  long-distance  infection 
is  also  effected  by  means  of  migratory  birds. 

There  are  a  number  of  facts  which  support  the  view  that  the  wind 
has  been  the  principal  agency  in  spreading  the  disease  over  the  present 
area.  For  instance,  trees  in  open  spaces  exposed  to  winds,  such  as 
those  along  roads,  at  the  edges  of  woods,  or  near  streams  or  ponds, 
are  apt  to  be  infected  sooner  than  the  trees  in  more  sheltered  situations ; 
trees  on  slopes  or  in  depressions  with  diseased  trees  on  higher  ground 
near  them  usually  become  infected,  evidently  because  they  have  been 
exposed  to  the  wind-scattered  spores  from  above;  and  in  thinned 
stands,  if  the  disease  is  present  in  the  neighborhood,  almost  every 
chestnut  becomes  affected.  In  this  instance  the  frequency  of  wounds 
is  probably  a  large  contributory  cause.  Dense  woods,  as  a  rule,  act 
as  a  bar  to  the  progress  of  the  infection,  except  where  the  disease  is 
very  prevalent  in  the  vicinity,  in  which  case  nothing  seems  to  check 
its  spread. 

AMOUNT  OF  DAMAGE. 

The  amount  of  loss  caused  by  this  disease  is  especially  great,  because 
it  has  developed  in  a  region  where  the  chestnut  trees  are  extensively 
used  for  ornamental  and  park  purposes.  For  this  reason  the  losses 
have  been  acutely  felt.  There  is,  of  course,  no  satisfactory  basis  for 
estimating  the  value  of  trees  which  are  useful  chiefly  for  aesthetic 
purposes,  but  the  loss  is  certainly  several  million  dollars. 


6 

In  Prospect  Park,  Brooklyn,  there  are  but  6  chestnut  trees  left 
alive  out  of  1,400.  In  Forest  Park,  at  Jamaica,  Long  Island,  practi- 
cally all  the  chestnut  trees  are  diseased  and  many  are  dead.  The 
same  applies  to  Bronx  Park  in  New  York  City.  In  Nassau  County, 
in  western  Long  Island,  few  chestnut  tracts  have  escaped  serious  dam- 
age. In  Westchester  County,  N.  Y.,  it  is  apparently  only  a  question 
of  a  short  time  when  nearly  all  the  chestnuts  will  be  destroyed.  Many 
estates  have  sustained  losses  in  scenic  beauty  which  it  is  impossible  to 
estimate.  In  the  part  of  New  Jersey  adjacent  to  New  York  City  the 
damage  has  been  of  the  same  character;  parks  and  country  estates 
have  lost  large  numbers  of  fine  chestnut  trees  which  would  not  ha'^e 
been  sold  at  any  price. 

Although  so  far  the  injury  to  ornamental  trees  has  attracted  the 
most  attention,  the  damage  is  not  confined  to  these  alone.  Indeed, 
a  far  more  serious  phase  of  the  epidemic  is  the  menace  to  commercial 
forest  tracts.  Already  many  large  tracts  in  at  least  five  States  have 
been  attacked,  and  though  great  damage  has  been  done  in  certain 
localities,  it  is  very  small  compared  with  what  it  will  be  if  the  disease 
continues  to  spread. 

A  favorable  feature  in  the  situation  is  that  so  far  the  disease  has 
done  most  damage  in  the  vicinity  of  the  sea,  and  there  are  some  indi- 
cations that  back  from  the  sea,  where  there  is  less  atmospheric  moist- 
ure, it  may  be  less  virulent  and  may  spread  less  rapidly. 

The  damage  which  would  result  from  the  destruction  or  extensive 
depreciation  of  the  commercial  chestnut  forests  would  be  many  times 
that  from  the  loss  of  ornamental  trees.  Chestnut  is  one  of  the  most 
rapidly  growing  and  most  useful  of  American  forest  trees,  and  it  plays  a 
very  important  part  in  the  forests  of  the  eastern  United  States.  The 
wood  is  exceedingly  durable  and  has,  therefore,  been  extensively  used 
for  posts,  poles,  and  railroad  ties,  while  its  grain,  color,  and  ease  of 
working  give  it  a  place  among  furniture  and  finishing  woods.  It  is, 
moreover,  a  very  vigorous  sprouter  and  lends  itself  admirably  to  for- 
est management.  With  the  exception  of  white  pine,  chestnut  proba- 
bly makes  the  moct  profitable  timber  crop  that  can  be  grown  in  the 
northeastern  part  of  the  United  States. 

XTTIIilZATION  OF  DEAD  AND  DISEASED  TREES. 

Since  the  fiuigus  does  not  work  in  the  wood  to  any  extent  and  ceases 
its  activities  when  the  tree  is  dead,  the  wood  is  not  damaged  as  a 
result  of  the  disease.  In  many  cases  only  a  part  of  the  tree  is  affected, 
while  the  rest  is  healthy  and  can  be  utilized  without  difficulty. 

Dead  trees  are  looked  upon  with  suspicion,  especially  if  they  are 
killed  by  a  disease,  and  the  wood  is  popularly  thought  to  be  weaker 
than  seasoned  live  timber.     In  the  case  of  this  fungus  there  is  no 


ground  for  such  a  prejudice;  as  a  matter  of  fact,  the  dead  material 
is  fully  as  strong  as  any  other  timber  if  it  is  utilized  within  a  few- 
years,  before  the  ordinary  agencies  of  decay  cause  it  to  deteriorate. 

In  most  of  the  places  where  the  disease  prevails  the  problem  of 
cutting  and  marketing  small  amounts  is  a  difficult  one.  The  dam- 
age from  the  disease  is  sudden  and  it  is  often  hard  to  find  a  market 
on  short  notice,  especially  for  small  quantities. 

In  order  to  market  the  material,  owners  should  encourage  the  con- 
tractors and  pole  buyers,  who  as  a  class  are  also  vitally  interested 
in  the  perpetuation  of  the  chestnut,  to  go  into  sections  where  the 
disease  is  doing  damage.  Where  the  tracts  are  large  enough  or  sev- 
eral are  located  close  together,  a  portable  sawmill  might  be  put  in. 
Where  the  quantity  of  chestnut  is  small,  the  best  disposal  is  for  ties, 
cord  wood,  and  fence  posts.  Owners  of  small  tracts  where  the  disease 
has  appeared  can  often  cooperate  to  great  advantage  in  order  to 
find  a  market  or  make  a  lumbering  operation  possible. 

MEASURES  OF  PREVENTION. 

The  chestnut  bark  disease  is  not  like  ordinary  fungous  diseases 
which  destroy  a  tree  here  and  there  after  a  number  of  years ;  it  is  even 
more  virulent  than  the  well-known  pear  blight,  which  it  resembles 
in  many  particulars.  It  destroys  quickly  and  'spreads  rapidly,  and 
it  is  of  the  utmost  importance  to  those  who  are  interested  in  chestnut 
forests  to  secure  a  means  of  checking  or  stamping  it  out  and  of  pre- 
venting its  spread  to  localities  which  are  as  yet  unaffected. 

Seedlings  and  sprouts  are  attacked  with  equal  virulence  and  old 
and  young  trees  are  killed  alike.  There  is,  therefore,  no  system  of 
forestry  which  can  be  used  to  control  the  disease.  Two  methods  of 
checking  its  spread  and  lessening  the  source  of  the  infection  are 
available : — 

1.  To  cut  out  the  diseased  trees.* 

2.  To  institute  a  quarantine  against  the  shipment  of  infected 
material. 

In  a  forest  tract  the  diseased  trees  should  be  cut  outright — all 
trees  which  show  the  least  sign  of  infection  should  be  removed.  In 
other  situations,  where  the  trees  have  a  peculiar  value,  it  may  be  pos- 
sible to  save  them  bycuttiiigoff  the  diseased  parts  only;  but  if  the 
trunk  of  a  tree  is  attacked,  the  whole  tree,  no  matter  how  valuable  it 
is,  should  be  cut  at  once,  for  it  is  practically  useless  to  try  to  save  it. 

Since  the  disease  generally  spreads  less  rapidly  m  dense  stands  than 
in  thin  ones,  it  will  often  be  possible  by  close  inspection  and  the 
prompt  removal  of  infected  trees  to  stamp  out  the  disease  altogether 
from  a  forest  tract.  For  the  same  reason,  however,  if  many  diseased 
trees  are  to  be  removed  and  their  removal  would  make  the  stand 
very  open,  it  will  often  be  better  to  make  a  clean  cut  of  all  the  chestnut. 


8 

All  diseased  bark  should  be  removed  and  burned.  After  that  is 
done  the  wood  is  practically  free  from  infection  and  can  be  used  or 
stored  with  safety. 

Even  greater  effort  should  be  directed  toward  preventing  the 
spread  of  the  disease  to  localities  which  are  as  yet  unaffected  than 
to  stamping  it  out  in  places  where  it  already  has  a  firm  hold.  . 

For  this  reason,  definite  legislation  seems  necessary,  and  it  is  very 
desirable  that  each  State  concerned  should  enact  a  law  providing  for 
a  quarantine  against  infected  chestnut  products,  chiefly  nursery- 
stock.  The  law  should  also  provide  for  systematic  and  thorough 
inspection  of  the  disease  and  require  the  cutting  out  of  infected  trees 
wherever  they  are  a  menace  to  healthy  stands  of  chestnut. 

The  nature  of  the  disease  and  the  necessity  of  fighting  it  should 
be  made  known  to  the  people  throughout  the  region  affected,  by 
means  of  the  press  and  by  enlisting  the  aid  of  the  granges  and  other 
organizations  interested. 

It  is  to  be  hoped  that  some  natural  limitation  to  the  destructive- 
ness  of  the  disease  may  be  found,  and  that  it  may  be  checked  by 
natural  causes.  But  its  rapid  spread  and  its  great  virulence  make 
waiting  dangerous.  Prompt  and  energetic  measures  should  be 
taken  to  stamp  it  out  wherever  it  appears. 

o 


